The present invention relates to a synchronous rotary cross cutter for cutting a material web of paper and the like.
More particularly, it relates to a synchronous cross cutter which includes two drums located at opposite sides of the path of the material web and synchronously rotatable about parallel axes, wherein each drum is provided with axially extending cutting elements arranged on the periphery of the drum, from which one of the cutting elements is formed or mounted elastically yieldably, and the cutting element of this pair is arranged with a certain two-sided overlap and produces at its one side a pulling cut in the plane of the path of the material web.
Rotary cross cutters of the above-mentioned general type are known in the art. In a known rotary cross cutter, the point of mutual contact of cross cutting elements moves during each cutting operation from one side of the material web to the other side of the latter, transversely to the longitudinal direction of the material web. In other words, the point of mutual contact travels from one side of the cutting element to the other side thereof. The cutting edges of the cutting elements do not extend parallel to the axes of the drums. Instead, they are turned at their periphery and produce thereby a shearing cut. The drums must rotate by a certain angle until the cut is carried out over the entire working width. During the cutting operation the cutting edges of the cutting elements lie on the contact point which moves transversely to the path of the material web, under pressure with spring action. However, during travelling of the angle of rotation, the geometrical position of the cutting elements relative to one another is changed. Thereby, the quality of cutting is also changed. This is especially disadvantageous for the cutting element which is formed or mounted in the drum elastically yieldable, since its free angle increases and thereby there is a tendency that it will be rigidly superimposed on the counter cutting element. This tendency increases with the wear of the cutting edge and can lead to breakage of portions of the cutting edges, and thereby to failure.